I like @PaigeMiller 's answer (LOGISTIC option in PROC POWER) but want to point out a particular pet peeve of mine. A post hoc calculation of power is pretty useless, except as a jumping off point for a planned future survey/experiment. Here is the reasoning that I was taught: You already know the p value of interest. Depending on your decision rule, then you either detected a difference (power=1) or you did not (power=0). It's why effect size is a major consideration in your interpretation of results.
So, as a prospective tool, you can use the effect size observed, a desired power or desired sample size, and an alpha level, you can calculate the remaining free variable. But that is for a collection of new samples from a population with characteristics similar to those in hand, not for the current sample from such a population. As I mentioned above, you already know the power for your current sample.
And you have to consider that the error estimates and point estimates from your weighted survey analysis have a built-in finite adjustment, which PROC POWER doesn't have. In my opinion, that means simulation is probably the best way to calculate prospective power/sample size.
SteveDenham
SteveDenham
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